Laminated container forming method and apparatus



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LAMINATED CONTAINER FORMING METHOD AND APPARATUS Original Filed July 20,1962 2 Sheets-Sheet 2 NH" 00000 g INVENTOR, Bryant Edwards BY TM 64%ATT'Y.

United States Patent 3,220,902 LAMINATED CONTAINER FORMING METHUD ANDAPPARATUS Bryant Edwards, Clarendon Hills, lll., assignor to IllinoisTool Works Inc, Chicago, 13]., a corporation of Delaware Continuation ofapplication Ser. No. 211,348, July 20, 1962, now Patent No. 3,141,595,dated July 21, 1964. This application May 5, 1964, Ser. No. 364,921

Claims. (Cl. 156-79) This application is a continuation-in-part ofapplication Serial No. 211,384 filed July 20, 1962, now Patent No.3,141,595 issued July 21, 1964.

This invention relates in general to containers, and more particularlyrelates to plastic containers which are of the thin wall variety and thematerials and methods by which the container is made.

It has long been desired to have an economical plastic container for usewith hot beverages, foods, etc., and of the type wherein the user is notsubjected to discomfort from heat transfer of the hot beverage or otheritems disposed in the container.

It is therefore the general object of this invention to provide aplastic container which, when filled with hot beverages, may be manuallygrasped without discomfort to the user while drinking from or carryingthe container.

Another object of this invention is to provide an economical plasticcontainer of the aforementioned type which may be stacked and readilydispensed from a vending machine, being comparable in weight to presentcup designs.

It is another object of this invention to provide a unitary plasticcontainer which is unaffected by humidity and thus is dimensionallystable for easy vending thereof, is uniform in size when manufactured bymass production techniques, and is otherwise well adapted to beautomatically vended from the vending machines now in use.

It is another object of this invention to provide a container asabove-described which is strong per unit weight, has no seams todisintegrate when filled with a hot beverage, and has a configurationaffording insulating characteristics such that it may be readily held bythe user when the temperature of the beverages or other items disposedwithin the container are well above the temperature that the human handcan normally withstand.

It is a further object of this invention to provide a novel container,as set forth above, which protects the table surfaces, etc., from heattransfer, and additionally the very low moisture vapor transmission ofthe material from which the container is made protects the tablesurfaces etc. from marking by the beverages contained therewithin.

Still another object of this invention is to provide a containercomparable in weight to container heretofore known, said container beingmade from laminated high density material and foam material wherein thefoam material aifords a greatly increased thickness of the container inthe area normally grasped by the user to thereby insulate the user fromthe temperature of the contents in the container without increasing thethickness of the entire article across its entire extent.

It is still another object of this invention to provide a container asaforedescribed wherein two dissimilar densities of material ofsubstantially identical chemical composition are laminated together andformed in a forming machine in a manner such that the laminate in thefinished container has a greater cross sectional thickness in the areanormally grasped by the user, the increased thickness in no wayimpairing the vending qualities of the container.

It is a further object of this invention to provide a novel method oflaminating foam plastic material to high density plastic material,expanding the foam portion of the laminate in a manner to rupture someof the foam cells immediately adjacent to the high density layer of the1aminate, and then by suitable machinery trap the gas liberated by therupturing of the cells so as to place the trapped gas in certainportions of the finally formed con; tainer that are normally grasped bythe user so as to increase the effective thickness of the container atthose portions which are normally grasped.

It is a further object of this invention to provide a container formingmethod wherein the material of laminated form is of such characteristicsthat the scrap from the molding machine may be readily re-ground andreconstituted for use in extruder machines, the laminate materialshaving similar chemical characteristics but differing densities.

A still further object of this invention is to provide an apparatus forlaminating together foam sheet material and high density sheet materialand then providing additional heating means so arranged and located soas to raise the temperature of the laminate in such a manner as torupture the foam cells immediately adjacent to the high density layer tothereby allow the disposition of the gas that is liberated intopreselected locations in the final forming of the container in a formingmachine.

Other objects and advantages of the present invention will appear in thefollowing description of the accompanying drawings wherein:

FIG. 1 is a semidiagrammatic view of an apparatus for molding aninsulated container of the type shown in FIG. 7;

FIG. 2 is a greatly enlarged sectional view of a portion of thelaminated sheet as indicated by the circle in FIG. 1;

FIG. 3 is a view similar to FIG. 2 showing a sectional view of thelaminated sheet after it has passed through the first heating means,said view being taken as indicated by a circle in FIG. 1;

FIG. 4 is a view similar to FIGS. 2 and 3 showing a greatly enlargedsectional view of still another portion of laminated sheet after it ispassed by the final heating means as indicated by the circle in FIG. 1;

FIG. 5 is a sectional view somewhat semidiagrammatic in form showing thelaminated material in the forming apparatus prior to the creation ofpressure differential across the sheet;

FIG. 6 is a greatly enlarged sectional view of the laminate at theindicated portion of FIG. 5;

FIG. 7 is an elevational view of an insulated container formed by thetechniques shown in the remaining figures;

FIG. 8 is a view similar to FIG. 5 showing the disposition of thelam-inate material after the imposition of a pressure differentialacross the laminate sheet;

FIG. 9 is an enlarged sectional view of the indicated portion of thecontainer formed in the mold as indicated in FIG. 8;

FIG. 10 is an enlarged fragmentary sectional view of the lower righthand corner portion of the container as indicated in FIG. 8; and

FIG. 11 is a view of the laminated sheet and the container side wall soformed when the laminated material is fed to the forming apparatus inreverse position to that shown and discussed in the foregoing figures,said view being an enlarged fragmentary sectional view of an areasimilar to that shown in FIG. 9.

Before discussing the invention in detail, some general background wouldappear beneficial. Plastic containers have begun to come into generaluse with automatic vending machines and (particularly when associatedwith hot beverages such as coffee, soup, etc.) presents a han dling orholding problem to the user when the beverage is served hot. Mostplastics used in manufacturing these containers have fairly goodinsulating characteristics per unit thickness when compared with othermaterials. However, in the interests of economical manufacture ofplastic containers to compete successfully with other materials,relatively thin walls are required. This obtains since raw plasticmaterial is uniformly sold on a per pound basis and increasing theamount or thickness of the material to increase the insulating qualitywould merely increase the unit price of a plastic container to make itnoncompetitive. One approach to the problem has been to try to extendthe plastic material by foaming, i.e., creating bubbles of gas in theplastic material and manufacturing a container of such foam material.However, foamed materials as such, while light in weight, and economicalin total amount of material used, normally have to be made too thick forready nestability of a plurality of containers one within the otherwhich is required for shipping a large volume of containers from themanufacturing plant to users. Further, foam material containers dentvery easily, do not provide the hard glossy surface often desired by theuser, and often do not have the required mechanical strength per unitthickness. Also, difficulties are often encountered in heating andprecisely handling foam material in forming. Heretofore, it has beendifficult to sheet form a foam sheet in high speed automatic formingmachinery. Thus, containers formed from straight foamed materials havenot comeinto wide spread commercial usage.

This invention deals with a laminate of foam material with high densitymaterial. The laminate preserves the advantages of both types ofmaterials and by the techniques to be discussed has some specialadvantages. One major advantage to the laminate is that it may behandled by sheet forming techniques.

In the instant application there is disclosed in semidiagrammatic form asheet forming technique which may be characterized as being acombination of mechanical plug assist and pressure differential. Whilethe instant invention has special advantages when made through the useof a mechanical plug assist and pressure differential technique, it willbe appreciated that it also has advantages relative to the other sheetforming techniques now in use such as vacuum forming, blow forming,drape forming, snap back forming and the various modifications thereof.As shall become apparent, the teachings of the instant technique haveapplication in any forming machinery of the sheet forming type whichutilizes a clamp means.

As shown in FIGURE 1, the apparatus utilizable to practice the method offorming an insulated container may comprise extruder means station 12, alaminating station 14, a first heater station 16, a second heaterstation 18, and a forming apparatus station 20. There is appropriatemeans 56 for transporting the laminated sheet between stations.

At the extruder means station 12 is a first extruder 22 denominated as asolid extruder which may be of any suitable and conventional type whichis adapted to extruded plastic material in sheet form and of desiredwidth and thickness. truder 22, it passes through suitable forming'rolls24 and 26 and comes out as a flat sheet 28. One particular plasticmaterial for sheet 28 is high impact polystyrene sheet having a densityof approximately 63 pounds per cu. ft. and a thickness of about .026inch. The second extruder means 30 shown diagrammatically as afoam'extruder is also located at the extruder means station 12 and isadapted to extrude a foam sheet 36 which passes through suitable formingrolls 32 and 34. The foam sheet 36 is preferably a low densitypolystyrene having a density of approximately 6 to 10 pounds per cu. ft.and having an initial thickness of approximately .060 inch. While bothextruders 22 and 30 are shown extruding and will be discussed in termsof extruding a polystyrene sheet material, it is to be remembered thatthe instant invention may be practiced with other different plasticmaterials having a As the material is extruded from the exsimilarchemical composition to each other which have both a high density sheetform and a second form which may be extended in such a manner as to formfoam cells. After the sheets 28 and 36 are extruded and have passed bytheir respective forming rolls, they may be preferably laminated at thelaminating station 14 by passing between suitable rolls 40 and 42. Aheater 44 may be disposed between the two sheets just immediately beforeentering the laminating station to provide sufficient heat for goodbonding lamination of the two sheets, if the heat of the individualsheets as they come from their respective extruders is not sufficient tocause a good bonding relation therebetween.

The laminate material 38 emanating from the laminating station 14 isshown in a greatly enlarged cross sectional view in FIGURE 2. Therelative dimensions aforediscussed relative to the two individual sheets28 and 36 making up the laminate 38 are shown in FIGURE 2, but it is tobe remembered that these dimensions are to be considered illustrativerather than limiting.

As the laminate 38 is moved from between the rolls 42 and 40, it may beeither stored in storage rolls or may be passed directly into theforming machinery. The dotted line 39 indicates Where the storage rolltake off would be placed if it is desired not to connect the extrudersdirectly to the forming machinery. As the laminate 38 is moved bytransporting means 56 toward the forming machinery, it passes throughthe first heating station 16. It is preferred that this heating stationcomprise upper and lower heaters 48 and 50, each of which may be a flameheater, electric-a1 heater, or infrared heat as suitable and desired.The heaters 48 and 50 above and below the sheet laminate 38 arecoordinated with the means 56 passing the sheet therebetween in such amanner that the amount of heat absorbed by the laminate 38 is sufficientto raise the temperature of both sides of the laminate, i.e., portions28 and 36 to the so called forming temperature of the foam portion 36 ofthe laminate. For the materials being discussed, i.e., the polystyrene,the forming temperature of the foam sheet 36 is in the neighborhood of215 F. By heating the laminate to 215 F., the laminate increases itsthickness, the material 36 expanding and becomes material 36a (seeFIGURE 3). The heat at station 16 causes the expansion of the gas in thefoam cells of material 36, the gas usually being air, so as to expandsheet 36 from its initial thickness of approximately .060 inch to adimension of approximately .090 inch, the dimensions of the high densitystyrene sheet 28 remaining approximately the same. As the sheettransporting means 56 continues to pass the material toward the formingmachinery, it passes by a second heating station 18. It will be apparentthat the second heating station 18 may be made integral with the firstheating station 16, assuming that the heat applying means is so arrangedand configured as to provide the net effect about to be discussed. Thesecond heating station has a heater 52 disposed relative to the laminateso that it heats the laminate 38 only from the side of the high densitymaterial 28. The heater 52 is so arranged relative to the movement ofthe sheet that the temperature of the sheet portion 28 of the laminateis raised to its forming temperature in the neighborhood of 250 F. Bythe application of additional heat at the heating station 18 from thesolid sheet side of the laminate, the migration of heat through thesheet 28 portion of the laminate 38a causes a rupture of the roam cellsimmediately adjacent to sheet 28. The ruptured .foam cells are shown at54 in FIGURE 4. Due to the rupture of the individual cells immediatelyadjacent to sheet 28, the laminate 38a effectively becomes a three layerlaminate 38b. The laminate 38b shown in cross section in FIGURE 4 nowhas the high density sheet material 28, a layer of ruptured cells 54 andthe nonruptured expanded cells 36a.

Due to the rupturing of the foam cell walls immediately adjacent to theboundary with sheet 28, there is migration freedom for the gaseousmaterial normally within the foam cells along the plane of the initialboundary of sheet 36a and sheet 28. Since the outer cells 36:: have notbeen ruptured and due to the fact that sheet 28 is not ruptured, therelatively free movement of air between the two layers is trappedtherebetween. Since it is conventional not to heat the extreme edges ofthe sheet for purposes of transporting, the air is effectively preventedfrom escaping from between layer 36a and layer 28. The three layerlaminate 38b has structural integrity because the ruptured portions ofthe foam cells still tend to adhere to the two sheets preventingcomplete separation. Material 38b now passes to the forming machineryfor molding into desired form.

As the laminate 38b is moved into the forming area of the formingmachinery, it is preferably handled in such a manner that it is firmlyclamped between upper and lower clamp means 58 and 60, which areassociated with upper mold means 62 and lower mold means 64respectively. It will be realized that while just a single cavity moldand clamp means are being discussed, multiple mold means are in factcontemplated, and the disclosure of the mold means is to be consideredsemi-diagrammatic only. In the instant forming machinery, the upper moldmeans 62 comprises a male plug member 66 have a sealing cut-off edge 68surrounding the upper end thereof for coaction with the lip 74 of thelower mold means 64 as shall become apparent. Means for creating apressure differential 70 is here shown as positive air pressure outletswhich are associated with the upper mold means 62; however, it will berealized that negative pressures or vacuum outlets associated with thelower mold means are equally contemplated. The lower mold means 64comprises a molding cavity 72 having an upper sealing cut-off lipportion 74 and a relatively movable knock-out plug 76. The upper lip 74coacts with portion 68 of the upper mold means as shown in FIGS. 5 and 8to first sealingly engage the laminate material around the moldingcavity and then later to act as a cut-01f if this is desired. Themolding cavity 72 is formed with a plurality of rings intermediate theheight of the cavity to provide radially inward projections 78 andgrooves or radially outward projections 79. These are shown in enlargeddetail in FIG. 9. The edges of the projection 78 and grooves 79 may beslightly rounded for manufacturing convenience purposes. It will benoted that the areas of the side walls joining the extremes of theprojections 78 and 79 have a back taper.

The steps of the forming process essentially comprise the clamping ofthe material 38b between the annular clamping means 58 and 60 and thusisolating the clamped area from the nonclamped area, mechanicallyprestretching the laminate 38b with the plug 66 until it reaches theposition shown in FIG. 5, then creating a pressure differential acrossthe web as by putting air under positive pressure through the apertures70 in the plug 66 to cause the material to expand to engage with thechilled cavity 72 having the projection 78 and grooves 79 therein. Thematerial then sets in its formed shape whereupon the mold means 62 and64 have further movement such that lip 74 and the edge 88 cut off theremaining material to make an article 80 such as shown in FIG. 7. Theknockout plug 76 then removes the article 80 from the mold and newmaterial 38b is automatically moved between the clamp means and themolding sequence continues.

Of particular note is the configuration of the side wall 86 of thecontainer 80 after it has been forced by the pressure differential intoengagement with the inward and outward projections 78 and 79 in themolding cavity. It will be noted that the thickness of the walls of thecontainer is not uniform as shown in enlarged section in FIG. 9. Asaforementioned, the area 54 immediately adjacent the common boundary ofthe two portions of the heated laminate 38b has gaseous material whichis free to migrate. The gas in area 54 cannot escape from the formingarea because of the clamp means 58 and 60. Thus, the

radially inner projections 78 of the mold when the material 38b isforced by the pressure differential into engagement therewith causesannular pockets between the projections preventing free migration of thetrapped gas. As the material of the laminate 38b engages any two axiallyspaced annular projections 78, the air or gas in the ruptured layer ofcells 54 is trapped between the two spaced projections. The radiallyoutward pressure being exerted by the pressure differential means 70 isresisted by this trapped air of layer 54 between the projections with aresilient back pressure. This in turn causes the radially outermostmaterial 28 of the laminate 38b to fill out the radially outermostprojections 79. The net effect of this is that the material in the sidewalls 86 of the container 80 formed by the radially outward projections79 becomes thicker at 82 than the rest of the container and considerablythicker than the portions 84 adjacent to the inward projections 78. Ithas been ascertained by direct measurement that the thickness of theside walls of the container at the portions indicated with the arrow 82exceed twice the thickness of the material at portions 84. Also thethickness of the side walls at 82 is more than twice the thickness ofthe lower portion of the side Walls 86 below the series of rings. Thethickness of the side walls of portion 82 in the finally formedcontainer 80 made as aforediscussed is in the vicinity of .0290 inch,portion 84 is in the vicinity of .0130 inch, and the side walls 86 belowthe rings is in the vicinity of .0125 inch. This construction greatlyaids the user grasping the side Wall of the container by insulating theuser from the contents of the container. Since the user contacts theouter side walls only at portions 82 formed by the grooves 79, the useris insulated from the exterior by the increased thickness of material.However, this location of the increased thickness of material at thesepredetermined points 82 on the side walls of the container does notadversely affect the nesting capabilities of the container.

As stated earlier, it is necessary and desirable that the insulatingcontainers be vendable and thus require close nesting. To this end,shoulder means 88 (shown in FIG. 10) is cooperable with an insideshoulder means 96 formed by angularly offset portions 90 and 94 on thenext adjacent cup to provide a stacking height for nesting of adjacentcontainers without jamming. Shoulder 88 while here shown spaced from thebottom wall 98 of the container may be, if desired, placed on thisbottom surface. It is important in forming an article of this type thatshoulder 94 be made of greater radial extent than is usually necessary.This radial extent of shoulder 94 causes a reduction of the thickness ofthe foam portion of the plastic material to provide an internal shoulder96 for cooperation with outside shoulder 88, i.e., the greaterhorizontal extent of portion 94 causes the foam material of the laminateto be relatively thin at that point disposed in immediately verticallyspaced relation to outer shoulder portion 88. It will be realized that,as shown in FIG. 10, all of the corner areas tend to be filled out byvirtue of the same effect that takes place in the side walls adjacent toprojections 78 and 79, this construction having the added additionalbenefit that a user grasping the container adjacent the bottom isbenefited by the greater insulating or thermal capacity in this area.

It will be particularly noted that the desirable effects of thisinvention are most greatly enhanced when the laminate 38b is so disposedto the mold means that the portion 28 of the laminate 38b engages theprojecting surfaces 78 first. When the reverse procedure is used, i.e.,the sheet 38b is fed to the mold means so that the foam engagesprojections 78 first, the result is as shown in FIG. 11. While there isan increase in the thickness of the material 82:: adjacent to theoutward projections 79 (as shown in FIG. 11) and portion 84a is thinnerthan portion 82a, the efiect is not as great, the difierence inthickness being in the neighborhood of one and one-half times. This,while effective for insulating purposes, is not 7 as beneficial in thisregard as the construction shown in FIG. 9.

Although specific embodiments of the invention have been shown anddescribed, it is with full awareness that many modifications thereof arepossible. The invention is thus not to be restricted except in so far asis necessitated by the prior art and by the spirit of the appendedclaims.

What is claimed as the invention is:

1. A method of forming an insulated article comprising the steps oflaminating an intumescent low density thermoplastic sheet of foammaterial to a relatively high density sheet of thermoplastic material,heating both sides of the laminate sheet to a temperature in thevicinity of the forming temperature of the low density thermoplasticmaterial, then heating the high density thermoplastic portion of thelaminate to a temperature sufiicient to rupture at least some of the lowdensity foam material in the vicinity of the initial boundary of saidsheets to allow movement of gaseous material liberated from saidruptured portion therebetwen, forming the heated material to an articleof desired configuration between opposed mold members, trapping thegaseous material between the sheets in preselected areas of said formedarticle by moving said preselected areas into engagement withprojections provided in one of said mold members to increase theeffective thickness and the insulating characteristics of said articlein said preselected areas, and thereafter chilling the formed article toprovide an article of insulated construction.

2. The method of forming an insulated article comprising the steps ofbondingly laminating a low density heat expansible cellularthermoplastic material in sheet form to a sheet of high densitythermoplastic material, heating the laminate to a first temperaturesufficient to further expand the low density thermoplastic material toclose to its maximum expansion without rupture of the cellular structurethereof, subsequently heating the high density side only of the laminateto a temperature sufficient to permit easy forming thereof andsufiicient to rupture a portion of the low density cellular materialimmediately adjacent the boundary to the solid density thermoplasticsheet material so as to create in effect a three layer laminatecomprising high density solid thermoplastic material, a layer ofruptured cells and a layer of nonruptured cells, clamping a discretearea of said three layer laminate with sufiicient force to prevent freemovement of gas in the ruptured layer from the discrete area within theclamping means to the exterior of the clamped area, forming the discreteclamped area into a desired shape by creating a pressure differentialacross the clamped area to conform the material to the shape of acomplementary mold, trapping gaseous material escaping from the rupturedlayer between at least two axially spaced circumferential shoulders ofsaid mold, chilling the formed shape, and separating the formed shapefrom the sheet to provide an insulated article.

3. The method set forth in claim 2 wherein the low density cellularsheet material as used in the laminated sheet has an initial thicknessgreater than the thickness of the high density sheet material, the lowdensity material having a weight in the vicinity of six to ten poundsper cu. ft., and the high density material having a weight in thevicinity of fifty to seventy pounds per cu. ft.

4. The method set forth in claim 2 wherein the forming step utilizesmolding apparatus which is configured with projections to form aplurality of projections in the side walls of the insulated container,said forming step including the contacting of the laminated materialwith the projections of the forming apparatus in a manner tending totrap gas intermediate the projections that is normally free to move inthe ruptured area of the laminate to in turn cause a greater relativethickness of material in the formed article in the area of theprojections in the side walls of the article. I

5. The method set forth in claim 2 wherein the low density material ispolystyrene foam sheet and the high density material is high impactpolystyrene sheet, the forming temperature of the foam sheet being inthe range of 200-230 F., the forming temperature of the high impactstyrene sheet being in the range of 231- 280 F.

6. The method set forth in claim 2 wherein the clamped material ismechanically predrawn by a plug means maintained at a temperaure nearthe temperature of the forming temperature of the low density materialand subsequently the preformed material is brought into contact with achilled mold means by a pressure differential across the clamped area toset the drawn material in its final shape.

7. The method set forth in claim 6 wherein the laminate is clamped in amanner such that the plug means engages the foam side of the laminateduring preforming and the solid high density portion of the laminateengages the chilled mold means upon creation of the pressuredifferential.

8. The method set forth in claim 6 wherein the solid high densitythermoplastic portion of the laminate engages the plug means during thepreform drawing of the material and the foam side of the laminateengages the chilled mold means upon creation of the pressuredilferential.

9. Apparatus for forming insulated containers comprising first extrudermeans extruding thin high density plastic material in sheet form havinga first thickness, second extruder means extruding foam plastic materialhaving a similar composition to said first-mentioned plastic materialalso in sheet foam and having a second thicknes greater than said firstthicknes, means including heater means associated with each of saidextruder means for laminating said foam sheet and said high densitysheet in integral bonded relationship, means for moving said laminatedsheet, first heating means adapted to heat both sides of said laminatedsheet to a predetermined temperature, additional heater means adapted toheat said high density side only of said laminated sheet to atemperature sufiicient to rupture at least some of the formed plasticmaterial in the vicinity of the common boundary of said sheets to allowmovement of gaseous material liberated from said ruptured portiontherebetween, and article forming means including clamping means forclamping a discrete area of the heated laminate means for causingengagement of the heated laminate with mold -means for forming anarticle of desired shape, and projection means in said mold means fortrapping the gaseous material in preselected areas of the formed articleto increase the effective thicknes and insulating characteristics of thearticle in said preselected areas.

10. The apparatus as set forth in claim 9 wherein said last mentionedmeans includes at least two spaced annular projections provided on saidmold means and being arranged to trap the gaseous material intermediatethe projections.

References Cited by the Examiner UNITED STATES PATENTS 2,338,490 1/1944Cunnington 15670 2,357,513 9/1944 Harmon 264-321 X 2,705,211 3/ 1955 DeWyk 15678 2,893,877 7/1959 Nickolls. 3,039,911 6/1962 Fox 264-321 X3,069,725 12/ 1962 Root 264-51 OTHER REFERENCES Collins, F. H.:Controlled Density Polystyrene Foam Extrustion, S.P.E. Journal, July1960, pp. 705-709.

I EARL M. BERGERT, Primary Examiner.

1. A METHOD OF FORMING AN INSULATED ARTICLE COMPRISING THE STEPS OFLAMINATING AN INTUMESCENT LOW DENSITY THERMOPLASTIC SHEET OF FOAMMATERIAL TO A RELATIVELY HIGH DENSITY SHEET OF THERMOPLASTIC MATERIAL,HEATING BOTH SIDES OF THE LAMINATE SHEET TO A TEMPERATURE IN THEVICINITY OF THE FORMING TEMPERATURE OF THE LOW DENSITY THERMOPLASTICMATERIAL, THEN HEATING THE HIGH DENSITY THERMOPLASTIC PORTION OF THELAMINATE TO A TEMPERATURE SUFFICIENT TO RUPTURE AT LEAST SOME OF THE LOWDENSITY FOAM MATERIAL IN THE VICINITY OF THE INITIAL BOUNDARY OF SAIDSHEETS TO ALLOW MOVEMENT OF GASEOUS MATERIAL LIBERATED FROM SAIDRUPTURED PORTION THEREBETWEEN, FORMING THE HEATED MATERIAL TO AN ARTICLEOF DESIRED CONFIGURATION BETWEEN OPPOSED MOLD MEMBERS, TRAPPING THEGASEOUS MATERIAL BETWEEN THE SHEETS IN PRESELECTED AREAS OF SAID FORMEDARTICLE BY MOVING SAID PRESELECTED AREAS INTO ENGAGEMENT WITHPROJECTIONS PROVIDED IN ONE OF SAID MOLD MEMBERS TO INCREASE THEEFFECTIVE THICKNESS AND THE INSULATING CHARACTERISTICS OF SAID ARTICLEIN SAID PRESELECTED AREAS, AND THEREAFTER CHILLING THE FORMED ARTICLE TOPROVIDE AN ARTICLE OF INSULATED CONSTRUCTION.